The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Conventional vehicular fuel systems, such as those installed in automobiles, may employ a “return fuel system” whereby a fuel supply tube is utilized to supply fuel to an engine and a fuel return line is utilized to return, hence “return fuel system,” unused fuel to a fuel tank. Such return fuel systems require the use of both, a supply line to and a return fuel line from the engine. More modern vehicles typically employ a “returnless fuel system” that may either be mechanically or electronically controlled.
Regarding such returnless fuel systems, such as a mechanical returnless fuel system (“MRFS”), only a fuel supply line from a fuel tank to an engine is utilized; therefore, no return fuel line from the engine to the fuel tank is necessary. As a result, a MRFS only delivers the volume of fuel required by an engine, regardless of the varying degree of the volume of fuel required; however, the fuel pump operates at 100% capacity irrespective of engine demand, with excess fuel being discharged through a fuel pump module via the pressure regulator. Because the fuel pump operates at 100% regardless of engine demand, more electrical energy is consumed than would be if the pump speed could be varied in accordance with such engine demand. Additionally, with the fuel pump operating at 100% of its speed capacity at all times, pump wear may be greater than if the pump operates at a fraction of its 100% speed capacity. Finally, noise, vibration and harshness are higher, especially at engine idle, than they otherwise would be if the fuel pump speed could be controlled. In a MRFS no interaction with an electronic control module or vehicle body control module occurs.
Electronic returnless fuel systems (“ERFS”) typically employ a pressure sensor in the engine fuel rail that communicates with a vehicle electronic control unit (“ECU”). The ECU may then communicate with a fuel pump controller which may use pulse width modulation (“PWM”), as an example, to control the voltage level across the fuel pump. By controlling the voltage level across the fuel pump, the pumping speed of the fuel pump, and accordingly its output volume, may be controlled. While such current MRFS and ERFS have generally proven to be satisfactory for their applications, each is associated with its share of limitations.
One limitation of current MRFS is that their fuel pumps operate at only one speed, that is, 100% of capacity, regardless of engine speed or engine fuel requirements. Operating in this manner may contribute to premature failure and necessary replacement of fuel pumps. Furthermore, noise, vibration and harshness, due to a fuel pump operating at 100% capacity at all times, is greater than a fuel pump that varies its speed. Additionally, at 100% capacity, the fuel pump draws a higher current and therefore diminishes fuel economy by placing a higher draw on the battery, and thus the alternator and consequently, on fuel consumption of the engine.
A limitation of current ERFS is that controlling the fuel pump is accomplished by using the vehicle ECU, and further communication with a fuel pump control unit. Such communication with a vehicle ECU requires extensive software programming and cross-coordination of engineering groups between fuel system suppliers and the supplier of the vehicle ECU. Furthermore, components such as exposed pressure sensors projecting from the fuel line at the engine are required and limit access to the engine by technicians or create an obstacle for adjacent parts.
What is needed then is a device that does not suffer from the above limitations. This, in turn, will provide a device that works similar to an MRFS, permits speed control of the fuel pump in accordance with engine fuel requirements, requires no cross-coordination with vehicle body ECU suppliers, does not require communication with a vehicle ECU, reduces consumption of electrical energy, and reduces noise, vibration and harshness.